I was diagnosed with polyneruopathy after a nerve conduction test and i think a emg . now my knee is swollen and hurting . what happens now ?

Find out why: Swollen knee is not directly related to peripheral neuropathy. You need to work up why you have peripheral neuropathy (? Diabetes, vitamin def, autoimmune dz, etc). The underlying cause may be related to your swollen knee.

Could be something: Serious. If you did not injure it, possibilities are gout, pseudogout, or infection. If you had an injury, it is probably bleeding from meniscus or ligament. Or it could be thrombophlebitis. Go see your doctor immediately.